All of the signatures in section 17.1 show the type constructor names prefixed with fn:. Should they not be prefixed with xs:?
Also, the very first signature example in the section has two prefixes:
fn:prefix:TYPE($arg as xs:anyAtomicType?) as prefix:TYPE?
which should presumably be just:
prefix:TYPE($arg as xs:anyAtomicType?) as prefix:TYPE?

Thanks for reporting this. I haven't quite got to the bottom of it yet, but it's a consequence of changes to the way function signatures are marked up in the XML source and processed using a pipeline of stylesheets.